1. Field of the Invention
This invention relates to a cooling method for electrical devices which require control of their operating temperature for effective functioning.
2. Background Art
Power can be distributed in many ways in electronic systems. Power distribution in a high current environment (e.g., 25-2,500 amps) requires moving the current from a power supply to various components, such as amplifiers, rectifiers, routers, servers, etc. Among the more common methods used are those that involve heavy gauge wire and cable, circuit boards, and copper bus bars.
Historically, solutions to power distribution have involved one or more heavy copper bus bars that are provided with holes for connecting cables. Typically, the bars might be spaced apart from each other and be isolated by insulating spacers. Large copper or aluminum bus bars and cables have been used for years to distribute power within industrial control and telecommunication cabinets. They are large and can carry high power relatively easily. Traditionally, if the bus bars became hot from excessive current, more air was moved within a cabinet to cool them. If the bars were uninsulated (and thus perilous to the touch), they tended to be located remotely for safety reasons. In such a setting, cables were run to connect the bars to the components.
Today, however, the quest continues for higher power in smaller packages. It would be desirable to engineer power distribution systems that can operate at higher temperatures so that more power can be distributed within a system.
Additionally, the packaging engineer contends with the problems of air flow and ventilation, vibration, noise, and efficient use of space.
In light of problems that are unsolved by previous approaches, it would be desirable to provide a cooling system for electrical components or conductors such as bus bars that increase the current-carrying capacity of the bus bar, while reducing its size, thereby saving space and weight.
Illustrative of prior art approaches is an evaporative spray coolant for cooling a heat source as described in U.S. Pat. No. 5,220,804, which issued on Jun. 22, 1993.
The invention is a method for increasing the capacity of an electrical component, such as a bus bar, to carry an electrical current. The method comprises the steps of exposing the electrical component to an evaporative fluid that is in fluid and thermal contact with the electrical component. A portion of the fluid undergoes a phase change to a vapor state. The hot component surface heats the fluid to its vaporization point. This results in an amount of heat transferred that is proportional to the latent heat of vaporization of the vaporized mass. Thus, heat generated by the flow of current is dissipated at least in part by the evaporative fluid. Accordingly, the temperature of the electrical component is maintained while carrying an increased electrical load because heat is dissipated at a rate comparable to that at which it is produced.